Question

What type of geometry and magnetic behaviour is found in compound [NiCl$_4$]$^{2-$? (Atomic no. Ni = 28)}

• A. Square planar and Paramagnetic
• B. Tetrahedral and paramagnetic
• C. Pyramidal and diamagnetic
• D. Square planar and paramagnetic

Hint:

Tetrahedral complexes with metal ions like Ni$^{2+}$ are often paramagnetic due to unpaired electrons in the d-orbitals.

Answer 1

The Correct Option is B

Step 1: Understanding the complex structure.
In the complex [NiCl$_4$]$^{2-}$, nickel is in the +2 oxidation state. Nickel in this state has an electron configuration of [Ar] 3d$^8$. The complex typically adopts a tetrahedral geometry. Due to the presence of unpaired electrons in the d-orbitals, the compound is paramagnetic.
Step 2: Analyzing the options.
(A) Square planar and Paramagnetic: This is incorrect because [NiCl$_4$]$^{2-}$ has a tetrahedral geometry, not square planar.
(B) Tetrahedral and paramagnetic: This is the correct answer, as [NiCl$_4$]$^{2-}$ adopts a tetrahedral geometry and is paramagnetic due to unpaired electrons.
(C) Pyramidal and diamagnetic: This is incorrect, as the geometry is tetrahedral, and the compound is paramagnetic, not diamagnetic.
(D) Square planar and paramagnetic: This is incorrect because the geometry is tetrahedral, not square planar.
Step 3: Conclusion.
The correct answer is (B) Tetrahedral and paramagnetic.